Fig. 6. The enlarged vesicles in the RabD^Q67L-expressing cells are the result of an increase in the rate of fusion between newly formed endo-lysosomes. Wild-type (A,C,E,G) and RabD^Q67L-expressing (B,D,F,H) cells were first pulsed with RITC-dextran for 5 minutes (C,D), washed, pulsed with FITC-dextran for 5 minutes (E,F), washed, chased for 5 minutes and gently fixed with formaldehyde. Captured images of cells were viewed in the fluorescein, rhodamine and merged channels. The extent of fusion between endo-lysosomes containing both fluors was measured in the wild-type (G) and RabD^Q67L-expressing (H) cells by detecting colocalization of both fluors in the same vesicle. Bar, 2.5 µm. The colored arrows indicate FITC-dextran-positive, RITC-dextran-positive and FITC/RITC-dextran-positive vesicles.